1. Field of the Invention
The present invention relates to a camera having a movable member, such as a lens group, which is movable to compensate for motion affecting the camera due to hand tremors of the photographer. More particularly, the present invention relates to a camera which sets the time at which the movable member begins to move, and which adjusts the movement of the movable member to compensate for motion originating in the camera.
2. Description of the Related Arts
Optical systems project an image onto an image place. Conventional image blur suppression devices suppress, or reduce, blurring of the image. A motion compensation device is a type of image blur suppression device, and compensates for motion incident upon the optical system.
Conventional cameras come equipped with motion compensation devices to compensate for motion incident upon the camera""s optical system. Such motion compensation devices are specifically designed to compensate for motion during photography caused by hand tremors of the photographer. For example, Japanese Laid Open Patent Publication No. HEI 2-66535 discloses a motion compensation device for a camera having a single-lens optical system. The motion compensation device detects changes in the angle of the camera""s optical axis generated by hand tremors, and uses the detected changes to compensate for motion caused by the hand tremors. In addition, Japanese Laid Open Patent Publication No. HEI 2-183217 discloses a motion compensation device which shifts part of an optical system of an internal focus telescopic lens, to compensate for motion caused by hand tremors.
Generally, a camera has a body device which communicates with a lens device. The camera includes a motion compensation device having a movable member inside the lens device. The lens device also includes a photographic optical system. To activate the motion compensation device, an activation signal is sent from the body device to the lens device. After receiving the activation signal, the motion compensation device moves the movable member to compensate for detected motion.
In a conventional motion compensation device, the movable member of the motion compensation device begins to move after a fixed amount of time from when the lens device receives the activation signal. Regardless of the motion waveform resulting from the hand tremors, the amount of time until the movable member begins to move, is fixed. As a result, delays in motion compensation occur when it is necessary to set the target speed of movement or the target acceleration of movement of the movable member to be relatively large due to a large amount of motion affecting the camera. For example, there is a large amount of motion affecting the camera at the start of film exposure. Therefore, motion compensation is inadequate at the start of film exposure since it is not possible to obtain the appropriate speed of movement of the movable member. As a result, highly accurate motion compensation control cannot be performed.
To obtain the appropriate speed of movement of the movable member at the start of film exposure, it is conceivable that the fixed amount of time to start movement of the movable member could be set to begin earlier. However, when movement of the movable member is started relatively early with respect to the start of film exposure, the movable member moves to the edge of its motion range at the start of film exposure. As a result, it is impossible to effectively use the entire motion range of the movable member, and highly accurate motion compensation control cannot be performed.
Moreover, motion compensation devices as disclosed in Japanese Patent Publications Nos. HEI 2-66535 and 2-183217 will be effected by additional problems when used in a single-lens reflex camera. In a single-lens reflex camera, brief, large amplitude motion occurs in the body device (to which the lens device is attached) due to mirror raising shock, shutter blade running vibration, drive vibration of the film winding motor, autofocus (AF) motor drive vibration and electrical noise. The motion compensation device will follow this brief, large amplitude motion originating in the body device. As a result, the motion compensation device cannot accurately follow and detect motion caused by hand tremors. Therefore, the motion compensation device cannot perform highly accurate motion compensation with respect to motion caused by hand tremors.
Accordingly, it is an object of the present invention to provide a camera having a motion compensation device which performs highly accurate motion compensation with respect to motion caused by hand tremors.
It is an additional object of the present invention to provide a camera having a motion compensation device which moves a movable member to compensate for motion on the camera, and optimizes the time at which movement of the movable member is started.
Objects of the present invention are achieved by providing an optical device, such as a camera, which performs an exposure operation to expose a recording medium. The optical device includes a movable member, and a control device for controlling the movable member. The movable member begins moving at an activation time prior to the exposure operation, and is then movable to compensate for motion affecting the optical device. The control device controls the movement of the movable member by detecting motion affecting the optical device and setting the activation time. The activation time is set so that, at the start of the exposure operation, the speed of movement of the movable member approximates the speed of movement of the detected motion. The control device can control the movement of the movable member by setting a target speed and/or a target acceleration of the movable member, so that, at the start of the exposure operation, the speed of the movable member approximates the speed of the detected motion. Further, the control device can detect motion by detecting the speed, acceleration and/or displacement of motion affecting the optical device.
Further, objects of the present invention are achieved by providing an optical device, such as a camera, which includes a movable member, an interrupt signal unit and a control device.
The movable member is movable to compensate for motion affecting the optical device. The interrupt signal unit produces an interrupt signal indicating when motion affecting the optical device originates in the optical device. The control device (a) detects motion affecting the optical device, (b) controls the movement of the movable member to compensate for the detected motion and, when the interrupt signal indicates that motion affecting the optical device originates in the optical device, (c) adjusts the movement of the movable member in accordance with the motion originating in the optical device. Further, when the interrupt signal indicates that motion affecting the optical device originates in the optical device, the control device controls the movable member to continue moving at the speed at which the movable member was moving immediately before the interrupt signal indicated that motion affecting the optical device originated in the optical device.
In addition, objects of the present invention are achieved by providing the optical device with a control device which (a) detects motion affecting the optical device, (b) controls the movement of the movable member to compensate for the detected motion and, when motion affecting the optical device originates in the optical device, (c) controls the movement of the movable member so that the movable member continues to move at the speed of movement at which the movable member was moving immediately before the motion affecting the optical device originated in the optical device.